Impact of extreme exercise at high altitude on oxidative stress in humans

Abstract

Exercise
and oxidative stress research continues to grow as a physiologic
sub-discipline. The influence of high altitude on exercise and oxidative
stress is among the recent topics of intense study in this area. Early
findings indicate that exercise at high altitude has an independent
influence on free radical generation and the resultant oxidative stress.
This review provides a detailed summary of oxidative stress
biochemistry as gleaned mainly from studies of humans exercising at high
altitude. Understanding of the human response to exercise at altitude
is largely derived from field-based research at altitudes above 3000m in
addition to laboratory studies which employ normobaric hypoxia. The
implications of oxidative stress incurred during high altitude exercise
appears to be a transient increase in oxidative damage followed by redox
sensitive adaptations in multiple tissues. These outcomes are
consistent for lowland natives, high altitude acclimated sojourners, and
highland natives, although the latter group exhibits a more robust
adaptive response. To date there is no evidence that altitude-induced
oxidative stress is deleterious to normal training or recovery
scenarios. Limited evidence suggests that deleterious outcomes related
to oxidative stress are limited to instances where individuals are
exposed to extreme elevations for extended durations. However,
confirmation of this tentative conclusion requires further
investigation. More applicably, altitude-induced hypoxia may have an
independent influence on redox sensitive adaptive responses to exercise
and exercise recovery. If correct, these findings may hold important
implications for athletes, mountaineers, and soldiers working at high
altitude. These points are raised within the confines of published
research on the topic of oxidative stress during exercise at altitude.